This invention relates in general to separation of solids from liquids and, in particular, to a microstrainer for separating or straining solids materials from the liquid to clarify the liquid and/or recover the solids materials.
More specifically, this invention relates to a microstraining system for separating solids materials from the liquid and removing the solids materials from the microstrainer in a semi-dry or damp state for further use or disposal.
Strainers in general have a wide variety of applications from waste water treatment to all types of industrial applications such as petrochemical, food processing, and materials processing. These applications cover a wide variety of functions from pipe lines to sophisticated engines, anywhere the solids materials may cause malfunction, damage, or must be removed for any other reason. While these strainers are utilized in many and varied applications, the strainers continuously become plugged with the material being separated from the liquid and, thereby, require extensive and expensive cleaning operations in order to maintain the screen in operation. These strainers frequently plug and require dismantling and cleaning of the screening material media which results in a breakdown of operation and high maintenance cost. Cleaning of the accumulated material from the screen requires that the unit be taken off line during cleaning of the screens. Removal of the unit off line interrupts the liquid-solid separation or requires that a second straining apparatus be used in order to provide a continuous uninterrupted separation system.
A number of screens or media have been developed to delay the plugging and to separate the solids mechanically for discharge. One of these is a sieve which incorporates a slotted or wedge construction of delta-type wires welded parallel to each other to form a series of slots. The triangular configuration of the wires allows the solids to go through the strainer after passing through the initial opening thereby preventing plugging. The slots are positioned with the opening in a horizontal position to allow actual rolling of the liquid-solids so that the liquid passes through the slots, but the solids material are rolled away following the screen curve to its lowermost point where they are discharged for disposal. While this type of screen or media is very effective, after a period of time the solids materials will accumulate on the surface plugging the openings and finally requiring that the equipment be cleaned.
Another type of microstraining system incorporates a rotating drum submerged in water to a predetermined level. The liquid to be clarified is passed through the interior of the drum and through the separating media which is installed on the inner peripheral surface. Solids are trapped inside the drum and on the screening media as the drum continuously rotates. At the uppermost portion of the drum interior the materials fall from the drum into a conveyor system utilized to transfer the solids from the interior of the drum for disposal. However, here again these apparatus encounter severe problems of plugging requiring frequent cleaning and high maintenance resulting in an almost prohibitive operating cost.